City Nature Challenge

CNC 2023

Started in 2016 as a competition between San Francisco and Los Angeles, the City Nature Challenge (CNC) has grown into an international event, motivating people around the world to find and document wildlife in their cities. Run by the Community Science teams at the California Academy of Sciences and the Natural History Museum of Los Angeles County, the CNC is an annual four-day global bioblitz at the end of April, where cities are in a collaboration-meets-friendly-competition to see not only what can be accomplished when we all work toward a common goal, but also which city can gather the most observations of nature, find the most species, and engage the most people in the event.

The majority of sightings are recorded using iNaturalist available as a free app or via the website. Visit iNaturalistUK or read more about how we use iNaturalist in the UK.

In the UK, we have been taking part since 2018 with Bristol leading the way. The term ‘city’ has also evolved over this period and includes wide urban areas eg Birmingham and the Black Country; the North East as well as City of Nottingham and Gloucester. The Natural History Consortium co-ordinates the UK’s involvement. Take a look at the CNC pages and wider website for information and resources.

Do you want to take part in 2027?

Next year’s City Nature Challenge is taking place from 30 April – 3 May 2027.

Would you like to find out more about becoming a City Nature Challenge Organiser for your city in 2027? Complete the sign up form which can be found on the City Nature Challenge participate page to register your interest. Please email the Natural History Consortium team at info@bnhc.org.uk to let them know you are signing up. They may be able to link you up with other people or groups who want to take part in your local area. They can also offer help and advice on what’s involved.

What happened in 2026?

The City Nature Challenge took place between Friday 24 April – Monday 27 April 2026. There were 754 cities in 61 countries on 6 continents participating!

Global 2026 Results

  • 76,422+ species documented
  • 3,001,825 observations recorded
  • 106,354 observers participated
  • 27,642 identifiers helped verify records
  • 754 cities across 61 countries took part, a record number of participating cities.
  • Most observed plant:Common dandelion
  • Most observed animal: Mallard

Notable UK highlights

In the UK, 28 urban areas took on the challenge. You can see the cities that took part and sort by observers, observations and species on the City Nature Challenge UK Leaderboard.

  • 161,927 observations
  • 5,061 species
  • 4,943 observers
  • 2,672 identifiers
  • York was the UK’s top city for recorded biodiversity, documenting 2,139 species, placing it among the top-performing cities globally for species richness.
  • London had the highest number of observations among the UK cities listed in the global leaderboard, with 20,974 records submitted by 836 observers.
  • York also contributed two species that were reported as first-ever global observations on iNaturalist: Arthonia protoparmeliopseos and Sporidesmium cambrense.

Download the infographic

See what happened across the UK in previous years.